JPS62138584A - Liquid crystal composition - Google Patents

Abstract

PURPOSE:To provide a GH type liquid crystal composition capable of GH type liquid crystal display with sharp contrast, high in solubility to the host liquid crystal (H), large in order parameter, containing, as the quest coloring matter (G), specific indigo coloring matter. CONSTITUTION:The objective liquid crystal composition containing as the quest coloring matter, at least one kind of indigo coloring matter of formula I [A and A' are each H, 1-3C alkyl or 2-4C acyl; R2 is branched alkyl or Z-R5 (R5 is cyclic alkyl, cyclic alkenyl or aryl; Z is 1-4C alkyl, N=N, O, S, NH, NHCO, etc). where, in case R2 is Z-R5, at least one of A and A' is not H; R1, R3 and R4 are each H, Cl, Br, No2, NH2, SR6 (R6 is 1-3C alkyl), CR6, etc.] The compound of the formula I can be prepared from a compound of formula II as the starting material, according to the reaction formula.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a guest-host type liquid crystal composition, particularly to a liquid crystal composition containing an indigo dye as a guest dye.

BACKGROUND ART A guest-host type (hereinafter referred to as GH type) liquid crystal display element uses a GH type liquid crystal composition in which a dichroic dye is added as a guest dye to a host liquid crystal as a matrix. As the host liquid crystal, a nematic liquid crystal, a chiral nematic liquid crystal, a cholesteric liquid crystal, a smectic liquid crystal, a chiral smectic liquid crystal, a smectic liquid crystal, etc. are used.

The contrast of the GH type liquid crystal display is S=(mul −5yo)/(mu〃+2muJ−)
It is governed by the order parameter S in the host liquid crystal of the dichroic dye, which is experimentally bundled by .

Here, A//+mu represents the absorbance of the dye when linearly polarized light parallel and perpendicular to the orientation force direction (director direction) of the host liquid crystal is incident, respectively. In a 5H type liquid crystal display element using a dye having parallel dichroism (P-type dye),
The closer the order parameter S is to 1, the higher the contrast can be displayed.0 In addition to the order parameter S, other characteristics required of pleochroic dyes used in GH type liquid crystal displays include high solubility in the host liquid crystal. In addition, it has excellent durability when used as a display element.

Conventionally, most of the pleochroic dyes for GH type liquid crystal displays have been azo and anthraquinone dyes, and dyes with various structures have been published01-≠)! -Despite the fact that indigo color pigments generally have excellent durability, there are no known pleochroic pigments that can be used in actual GH-type liquid crystal displays0 Problems to be Solved by the Invention When using indigo dyes as dichroic dyes for GH type liquid crystal displays, the biggest problem is that they have very low solubility in host liquid crystals. Therefore, a GH type liquid crystal composition in which an indigo dye is dissolved has almost no color and cannot be used for a GH type liquid crystal display.

The present invention improves the solubility of an indigo dye in a host liquid crystal to obtain a sufficient coloring state for a GH type liquid crystal display, and also improves the order parameter S in the host liquid crystal.
The object of the present invention is to obtain a GH-type liquid crystal composition that enables high-contrast GH-type liquid crystal display by increasing the contrast.

Means for Solving the Problems An indigo dye having a structure represented by the following general formula (1) is used as a guest dye to be dissolved in a host liquid crystal.

(In the formula, A and A' each independently represent hydrogen, an alkyl group having 1 to 3 carbon atoms, or an acyl group having 2 to 4 carbon atoms, and R2 is a branched alkyl group or Z-R5 (R5
represents a cyclic alkyl group, a cyclic alkenyl group, or an aryl group, 2 is a bond, and a saturated or unsaturated alkyl chain having 1 to 4 carbon atoms.

N=N, O, S, NH, NHCO, Coo or C0N
0) representing H (however, if R2 is 2-R5, at least one of M and A' is not hydrogen). R+ +
R5+ R4+ is hydrogen, Cjl.

OR6, GOOR6, CoR6, NHCOR6, CON
It represents a H2° group, and R7 represents hydrogen or an alkyl group having 1 to 3 carbon atoms. ) or a combination of two or more thereof. ) Effect: The indigo dye used in the present invention has a molecular structure represented by the general formula [1], has high solubility in the host liquid crystal, and has a high order parameter S.

In other words, unsubstituted indigo has very low solubility, but the solubility can be improved by replacing the hydrogen of the amino group in the indigo skeleton with an alkyl group or acyl group, or by introducing a branched alkyl group into the benzene ring of the indigo skeleton. can be increased. In addition, the transition moment direction of light absorption has approximately one value of 5
The order parameter S can be increased by introducing substituents at the 5' and 5' positions to extend the long axis of the molecule in this direction. By using such indigo dyes, it is possible to produce G with excellent coloring properties and high contrast.
A GH type liquid crystal composition capable of H type liquid crystal display is obtained.

Here, preferred examples of R2 in the general formula (1) are listed below.

(1) Branched alkyl group having 3 to 10 carbon atoms or Z-
R8 (R8 represents a substituted cyclohexyl group, a substituted cyclohexenyl group, or a substituted phenyl group, 2 is a bond, a saturated or unsaturated alkyl chain having 1 to 4 carbon atoms, N=N,
O, S, NH.

Represents NHCO, Coo or CONH. )(2) Branched alkyl group having 3 to 10 carbon atoms and branched at the carbon directly bonded to the benzene ring of the dye skeleton (3) Z R9
(R9 represents an alkyl group having 1 to 8 carbon atoms, an alkoxy group, an alkylthio group, a substituted cyclohexyl group, a substituted cyclohexenyl group, or a cyclohexyl group substituted with an aryl group at the 4-position, a cyclohexenyl group, or a phenyl group, Z is a bond, a saturated or unsaturated alkyl chain having 1 to 4 carbon atoms, N=N, O, S.

NH, NHCO, (represents joot or C0NH)
(4) Tertiary alkyl group having 4 to 10 carbon atoms branched at carbon directly bonded to the benzene ring of the dye skeleton (5) Z
R10 (Rho is a75 having 1 to 8 carbon atoms at the 4th position; represents a substituted cyclohexyl group, cyclohexenyl group, or phenyl group, 2 is a bond, a saturated or unsaturated alkyl chain having 1 to 4 carbon atoms) .

N=N, O, S, NH, NHCO, Coo or G
Represents ONH. ) (6) Y R11 (Ra1 represents a trans-cyclohexyl group, a cyclohexenyl group, or a phenyl group substituted with an alkyl group having 1 to 8 carbon atoms, an alkoxy group, or an alkylthio group at the 4-position, and Y represents a bond. Examples Among the indigo dyes represented by the general formula (1) used in the present invention, the indigo skeleton amino group is not substituted with an alkyl group or an acyl group (in the general formula (1), A two' = hydrogen) can be synthesized, for example, by the route shown below.

(Left below) CID [1)i4 [■] (In the formula, R1, R2, R5+ R4 represent the above meanings, and M and A' are hydrogen.) The general formula obtained in this way In the indigo dye represented by [I], the substituents A and A' of the dye backbone amino group are hydrogen, but by reacting with a suitable alkylating agent or acylating agent, alkylation can be performed, for example, as shown below. Alternatively, acylation can be performed.

(In the formula, R represents an alkyl group, and X represents ).logen. In addition, when the skeleton benzene ring in (1) has hydrogen, modification by halogenation, nitration, etc. is possible.

The compound represented by the general formula (II, l, [HI,) is
For example, it can be obtained by a known method using the route shown in % below.

(Margin below) The indigo dye used in the present invention thus obtained has excellent solubility in the host liquid crystal and has a high order parameter S. The present invention will be described below with reference to specific examples.

Example 1 (Margin below) (6-t-Amyl-2-aminophenyl)glyoxal dimethyl acetal 5,309 was dissolved in 100 mJ of glacial acetic acid, 20 ml of concentrated sulfuric acid was added, and the mixture was heated for 30 minutes. After cooling, 1 ooml of water was added, and the resulting precipitate was filtered, washed with water, and then dried. It was purified by chloroform-silica gel column chromatography and recrystallized from hexane-chloroform to obtain 1.17 g of crystals of indigo dye (1). Structural confirmation was performed using NMR, IR, elemental analysis, and mass spectrometry. 0 (6-1-Amyl-2-aminophenyl) glyoxal dimethyl acetal can be obtained from 4-t-amylaniline by the above-mentioned synthetic route. I can do it.

(hereinafter referred to as Kinshiro) Example 2 C5-(4-1-lanse-propylcyclohexyl)-
Dissolve 3.20 g of 2-aminophenyl glyoxal dimethyl acetal in glacial acetic acid-ROML, and add 1 liter of concentrated sulfuric acid.
Add rni and heat for 30 minutes. After cooling, 100m of water
A precipitate formed by adding g was filtered out, washed with water, and then dried. After purification by dichloroethane-silica gel column chromatography, the product was recrystallized from toluene to obtain 0.67 g of (2). Structure confirmation was performed in the same manner as in Example 1.

(s-(4-trans-propylcyclohexyl)-2
-Aminophenyl]glyoxal dimethyl acetal can be obtained from 4-(4-trans-propylcyclohexyl)aniline according to the synthetic route described above.

Example 3 The following compounds were obtained in the same manner as in this Example Example 1. ts of indigo dye (10) obtained in Example 2
4 mg of ts was dissolved in 50 ml of anhydrous N,N-dimethylformamide, a slight excess of sodium hydride was added, and the mixture was stirred at room temperature for about 3 hours to extract hydrogen from the amine group to form a sodium salt. With excess methyl iodide and at room temperature approx.
After leaving the mixture at room temperature for an hour, the reaction mixture was poured into an aqueous ammonium chloride solution, and the precipitate was filtered and washed with water. After purification by silica gel column chromatography, it was recrystallized from benzene-hexane to obtain dye ζ15)208m,j7. The structure was confirmed in the same manner as in Example 1.

Similarly, by the reaction of (2) and (3) with methyl iodide, θ
e), (17) was reacted with (5), (,9) and ethyl iodide to obtain 18.190 Example 4 (2o) Example 1. Indigo dye C3) 374 obtained in Example 2
mg of propionyl chloride in 10 mj of n-butyl acetate, s ml and 0.5 r of 2,6-lutidine.
Add nl and react at 100'C for 15 hours without stirring. n-Butyl acetate was distilled off under reduced pressure, and the residue was dissolved in benzene and filtered to remove insoluble lutidine hydrochloride. The filtrate was concentrated, purified by benzene-silica gel column chromatography, and then recrystallized from chloroform-ethanol to obtain 183 ml of dye 120). Structure confirmation was performed in the same manner as in Example 1.

Similarly, (2>, (4) is reacted with acetyl chloride to obtain (21) and (22>), and (8), (11)
By the reaction of and propionyl chloride (2a), (
243 was obtained Example 6 The dye ζ6) of Example 1.2 was dissolved in O,a weight percent in a liquid crystal mixture ZLI-1586 commercially available from Merck & Co., and this liquid crystal composition was applied to a gear of about 10 μm between the substrates. It was sealed in a homogeneous orientation cell.

The order parameter S was calculated by measuring the absorbance A// and AJL at the maximum absorption wavelength of 61 nm for linearly polarized light parallel and perpendicular to the orientation direction of the liquid crystal, and using the above-mentioned relational expression (% formula %).

A// at the maximum absorption wavelength is 1.021, Am
was 0.157. Therefore, the order parameter S of dye (5) is 0.66.

When the teno order parameter S in the dye (1) OZLI-1s was measured in the same way, S=0.66
Example 6 The absorbance of the dye L16) of Example 3 at a maximum absorption wavelength of 643 nm was measured in the same manner as in Example 5 in the liquid crystal mixture ZLI-2444 commercially available from Merck & Co., and the order parameter S was determined. The determined 0 dye concentration is 1.2% by weight, A
〃 was 1.103, A was 0.112, and the order parameter S was 0.75.

Similarly, for dyes (15) and (18) of Example 30, Z
When the order parameter S was determined in LI-2444, it was 0.74 and 0.62, respectively.

Example 7 The dye (2o) of Example 4 was dissolved in ZLI-1565 in an amount of 0.9% by weight, and in the same manner as in Example 5, the absorbance at the maximum absorption wavelength of 572 nm was measured and the order parameter S was calculated. A// at this wavelength is 0,731. A is 0.132, and the order parameter S is 0.60
Met.

Similarly, regarding the dye (21) of Example 4, ZLI-156
Calculating the order parameter S in 6, 3 = 0.
It was 74.

As shown in Examples 6 and 6.7, the indigo dye used in the present invention exhibits good dichroism with order parameters s>o and e, and in particular, the indigo dye used in the present invention exhibits good dichroism, especially when the 4-substituted phenyl group and trans-4-substituted cyclohexyl group The dye with S>0.7 shows a very high order parameter, and has a high contrast G
H-type liquid crystal display is possible.

Example 8 As a comparative example, an unsubstituted indigo compound 6) was heated and dissolved in ZLI-, left for two weeks at room temperature, and the precipitate was filtered to prepare a saturated solution. When the sample was sealed, no coloring was observed at all. - The indigo dye used in the strength wood invention is used when the gap between the substrates is 10μ as shown in Example 5.6゜7.
Even if the liquid crystal composition is sealed in a cell of m, a liquid crystal composition with a sufficient concentration for order parameter measurement can be obtained. Indigo skeleton benzene moderate IF 4 Sho 4 + Maru Shichi M - Nuki Komochi 1 U 71 - Death Recommendation By introducing an alkyl group or an acyl group to the mino group, the solubility is greatly improved and it is sufficient for GH type liquid crystal display. A concentrated liquid crystal composition is obtained.

Effects of the Invention The indigo dye used in the present invention has high solubility in host liquid crystals and large order parameters, and is therefore very useful as a dichroic dye that can be used in guest-0-host type liquid crystal displays with good contrast.

Claims (7)

[Claims] (1) As a guest dye, the following general formula [I] ▲Mathematical formula, chemical formula, table, etc.▼[I] (In the formula, A and A' are each independently hydrogen, carbon number 1
~3 alkyl groups or acyl groups having 2 to 4 carbon atoms, R_2 is a branched alkyl group or Z-R_5 (R
_5 represents a cyclic alkyl group, a cyclic alkenyl group, or an aryl group, Z is a bond, a saturated or unsaturated alkyl chain having 1 to 4 carbon atoms, N=N, O, S, NH, NHC
Represents O, COO or CONH. ) represents (however,
When R_2 is Z-R_5, at least one of A and A' is not hydrogen. ). R_1, R_3, R_4 are hydrogen, Cl, Br, R_6, NO_2, NH_2, ▲ formula,
There are chemical formulas, tables, etc. ▼, SR_6, OR_6, CO
OR_6, COR_6, NHCOR_6, CONH_2
, ▲Mathematical formulas, chemical formulas, tables, etc.▼ (R_6 represents an alkyl group with 1 to 3 carbon atoms, R_7 represents hydrogen or an alkyl group with 1 to 3 carbon atoms), or any of these Represents a combination of two or more types. ) A liquid crystal composition containing at least one type of indigo dye represented by: (2) R_2 is a branched alkyl group having 3 to 10 carbon atoms or Z-R_8 (R_8 represents a substituted cyclohexyl group, substituted cyclohexenyl group, or substituted phenyl group, Z is a bond, and has 1 to 4 carbon atoms) saturated or unsaturated alkyl chain, N=N, O, S, NH, NHCO, COO or C
Represents ONH. ) The liquid crystal composition according to claim 1. (3) The liquid crystal composition according to claim 2, wherein R_2 is a branched alkyl group having 3 to 10 carbon atoms that is branched at a carbon directly bonded to the benzene ring of the dye skeleton. (4) R_2 is Z-R_9 (R_9 is a cyclohexyl group substituted with an alkyl group having 1 to 8 carbon atoms, an alkoxy group, an alkylthio group, a substituted cyclohexyl group, a substituted cyclohexenyl group, or an aryl group in at least the 4th position, cyclohexenyl group or phenyl group, Z is a bond,
Saturated or unsaturated alkyl chain having 1 to 4 carbon atoms, N=
Represents N, O, S, NH, NHCO, COO or CONH. ) The liquid crystal composition according to claim 2. (5) The liquid crystal composition according to claim 3, wherein R_2 is a tertiary alkyl group having 4 to 10 carbon atoms and branched at a carbon directly bonded to the benzene ring of the dye skeleton. (6) R_2 is Z-R_1_0 (R_1_0 represents a cyclohexyl group, a cyclohexenyl group, or a phenyl group substituted with an alkyl group having 1 to 8 carbon atoms, an alkoxy group, or an alkylthio group at the 4th position, and Z is a bond, a carbon Number 1~
4 saturated or unsaturated alkyl chains, N=N, O, S
, NH, NHCO, COO or CONH. ) The liquid crystal composition according to claim 4. (7) R_2 is Y-R_1_1 (R_1_1 represents a trans-cyclohexyl group, cyclohexenyl group, or phenyl group substituted with an alkyl group, alkoxy group, or alkylthio group having 1 to 8 carbon atoms at the 4th position, and Y is a bond 7. The liquid crystal composition according to claim 6.